Optical switching elements have been sought for some time, and a variety of different techniques have been proposed. For example, U.S. Pat. No. 4,040,718 issued to G. C. Bjorklund et al on Aug. 8, 1977 employs the dispersion caused by a two-photon transition to rotate a polarized beam of light between crossed polarizers.
Color centers in crystals have been used to generate light in a distributed feedback laser, but not to switch or to diffract radiation of a wavelength different from that generated by the color centers. (See U.S. Pat. No. 3,991,386 issued to G. C. Bjorklund et al on November 9, 1976, incorporated herein by reference.)